E a s i l y M i s s e d Fr a c t u re s o f t h e Up p e r E x t rem i t y Scott Tyson, MD, Stephen F. Hatem, MD* KEYWORDS  Fracture  Upper extremity  Missed diagnosis  Diagnostic error


INTRODUCTION Interpretation of radiographs may not have the glamour of newer, high-tech imaging techniques, but remains the staple in the evaluation for acute orthopedic injury. It is difficult: experimental studies spanning a half century have consistently documented a roughly 30% error rate in radiographic interpretation.1 “Misses” may result in a delay in diagnosis, increased patient pain and suffering, and delay in appropriate therapy.2 Detriment may not be limited to the patient; in addition to emotional angst, disbelief, and self-doubt, radiologists may be faced with a claim of malpractice. In a recent review of closed malpractice claims in the United States, radiology was the sixth most frequent specialty despite making up less than 5% of United States physicians.3 Nearly 3 out of 4 claims against diagnostic radiologists cite errors in interpretation resulting in missed diagnoses.1 A 2013 study found that claims against radiologists related to an error in diagnosis outpaced the next most common cause by nearly 10-fold.3 Interpretation errors in radiology can broadly be classified into 2 categories: cognitive and perceptual. Cognitive errors might be owing to a lack of knowledge or mistaken judgment, for example, and are the minority. Perceptual errors, in which an abnormality is simply not seen, account for up

to 80% of radiologic errors.4 Perceptual errors in the identification of fractures are related to many factors, including not just the subtlety of the finding,2,5 but the amount of clinical information available,1 technical factors such as the quality of the images and the views obtained,1 and poorly understood factors seemingly inherent to “human nature.”5 Given that diagnostic errors in skeletal radiology, along with mammography, are the leading causes of claims against radiologists,1,3 it is unsurprising that missed fractures are a particular problem in emergency and trauma care. A recent Canadian study showed that fractures accounted for 70% of missed injuries in a level 1 trauma center.6 Another study has shown emergency physicians’ radiographic interpretations for fracture had an 8% false-negative rate.7 Missed fractures also were the most common discrepancy upon staff review of radiology resident interpretations for the emergency department, accounting for 62.5% in a recent study.8 This is in keeping with other studies, which have shown that 70% of missed fractures are identifiable in retrospect.2 In addition, radiologists may change their own interpretations up to 20% of the time.9 These observations suggest that there may be ways to improve performance, and a recent study has shown just that: Itri and colleagues10 were able to decrease

Department of Radiology, Imaging Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk A-21, Cleveland, OH 44195, USA * Corresponding author. E-mail address: [email protected] Radiol Clin N Am 53 (2015) 717–736 http://dx.doi.org/10.1016/j.rcl.2015.02.013 0033-8389/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.


 Radiographs remain the mainstay for fracture assessment; their assessment remains challenging.  Error rates can decrease by review of missed fractures.  Three categories of challenging injuries are reviewed: common but challenging; out of mind, out of sight; and satisfaction of search.


Tyson & Hatem resident misinterpretation of musculoskeletal emergency films at the Hospital of the University of Pennsylvania after giving a series of upper and lower extremity focused missed case conferences. In 1 year, resident misinterpretations of shoulder and elbow injuries decreased by 80%.10 We prefer to think of this as cognitive training to minimize perceptual error: it is easier to see what you know to look for, and easy to miss what you do not. Knowledge of what is missed is paramount, because it allows the generalization of what one learns from his own errors to others. Thankfully, there is a wealth of quality information available on missed fractures in the emergency department, whether by emergency physicians, radiology residents, or staff radiologists. With respect to the subject at hand, upper extremity fractures consistently have accounted for just under one-half (43%–48%) of all missed fractures independent of the group of readers investigated.2,7,8 A closer look at these studies provides a road map both for what to look for when interpreting films and for this review, with the goal of minimizing errors. The Wei and colleagues2 study included more than 3000 extremity fractures. One hundred fifteen missed fractures were identified for an overall missed fracture rate of 3.7%, in keeping with other reports.4 Subtlety (37%) and imperceptibility (33%) were by far the most common reasons. Less common reasons were obscuring devices and artifacts, multiplicity, osteoporosis, lack of clinical information, and poor technique. It is noteworthy that 5% of the misses were later diagnosed using specialized views, underscoring the importance of knowing how to supplement or tailor the radiographic study to the question at hand. The rate of missed extremity fractures was similar between the upper and lower extremity. Nearly one-third (30.4%) of all missed extremity fractures were in the hand and wrist, and these sites accounted for nearly 2 out of 3 (65%) of missed upper extremity fractures. Per anatomic site, however, fractures were most likely to be missed in the following order: elbow (6.0%) more often than hand (5.4%) more often than wrist (4.1%) more often than shoulder (1.9%). Of upper extremity fractures missed even on retrospective review, the distal radius was the most common site. Including missed proximal radius fractures at the elbow, the radius alone accounted for one-third of missed diagnoses. Other retrospectively missed upper extremity fracture sites included the clavicle, humeral head, distal humerus, olecranon, scaphoid, hamate, trapezium, ulnar styloid, and phalanges. Similar results were reported by Kung and colleagues.8 Fractures were missed by radiology

residents in the upper extremity in 1.6% of patients, slightly more than in the lower extremity. The radius as a whole accounted for one-half (50%) of these, split between the head and distally. Sixty-four percent were in the hand and wrist, with other sites of misses including the clavicle, humerus, triquetrum, metacarpals, and phalanges. Misinterpretation of hand and wrist films for fracture was also the leading cause of misdiagnosis in a study of emergency physician interpretations.7 In addition to this foreknowledge of the injuries likely to be missed on radiographs, optimizing clinical information, radiographic technique, and views are all important to improving diagnostic performance. In each, the radiology technologist can play a valuable role. With adequate clinical history and high-quality images, attention can be directed to the basics of fracture evaluation at the appropriate sites: cortical disruption, buckling, or crimping; lucent fracture lines; sclerotic fracture lines (overlap, impaction, or intramedullary callus); and double densities owing to overlap by displaced fragments. Careful attention to soft tissue findings such as swelling, laceration, or effusion can direct attention to the injured area. Our review of easily missed upper extremity fractures in adults emphasizes the following 3 categories of pitfalls, with particular attention to their epidemiology, imaging findings, and optimal radiographic evaluation:  “Common but challenging”: we know to look for it but the findings may be subtle  “Out of mind, out of sight”: the uncommon injuries that are beyond the normal search pattern and hence, “out of mind”  “Satisfaction of search”: the less common or more diagnostically challenging injuries that occur in association with more obvious ones.

COMMON BUT CHALLENGING Isolated Fracture of the Greater Tuberosity of the Humerus Almost one-half of all humeral fractures involve the proximal humerus, with isolated greater tuberosity fractures comprising about 20% of all proximal humeral fractures (Fig. 1).11,12 Unlike other proximal humerus fractures, which generally affect older populations with medical comorbidities, isolated greater tuberosity fractures tend to affect younger, healthier patients. In a reported series of 610 proximal humeral fractures, Kim and colleagues13 compared demographics of patients with isolated greater tuberosity fractures with all other proximal humerus fractures, and showed that mean age

Easily Missed Fractures of the Upper Extremity

Fig. 1. Greater tuberosity fracture. Shoulder pain 2 months after a fall. (A) Fat-suppressed proton density weighted oblique coronal MR imaging and (B) true anteroposterior (AP) view with external rotation. Initial (C) AP internal rotation and (D) true AP external rotation radiographs. MR imaging (A) obtained to evaluate for rotator cuff tear shows nondisplaced linear fracture (arrow) of the greater tuberosity with surrounding bone marrow edema. (B) True AP shoulder radiograph with external rotation of the humerus confirmed the fracture (arrow) with typical resorption about the fracture in the subacute phase of healing. (C, D) Initially interpreted as normal, in retrospect subtle greater tuberosity fracture with cortical disruption (arrow) is more apparent on the external rotation view with the greater tuberosity seen in profile. In internal rotation, there is a very subtle double density (dashed oval).

(42.8 years greater tuberosity fractures vs 54.2 years all others) differed significantly. Traditionally, greater tuberosity fractures have been described as either impaction or shear/avulsion injuries.11,14 Impaction may result from direct trauma to the tuberosity or from impaction against the acromion or superior glenoid with the arm in hyperabduction. Shear/avulsion injury typically occurs in association with anterior glenohumeral dislocation. As the humeral head is displaced forward, the rotator cuff counteracts this force, resulting in avulsion of the greater tuberosity. Despite being a well-recognized clinical entity, isolated greater tuberosity fractures are missed commonly. Ogawa and colleagues15 reported a series in which 58 of 99 shoulders (59%) with confirmed isolated fracture of the greater tuberosity that had been overlooked initially. The majority of these were isolated to the supraspinatus facet.15 The failure to recognize the fracture

initially can lead the clinician to an alternative and incorrect diagnosis, and ultimately lead to a poor clinical outcome. Nondisplaced greater tuberosity fractures are not uncommonly diagnosed on MR imaging obtained for suspected posttraumatic rotator cuff tear, owing to pain at the greater tuberosity and with abduction.16 When a greater tuberosity fracture is identified, treatment is guided by the amount of displacement of the fracture fragment. Although guidelines vary, most authors advocate for surgical treatment for fractures displaced by greater than 5 mm in the general population, and by greater than 3 mm in younger patients and athletes.14,17 Evaluation of acute shoulder injury typically culminates with radiographic examination. Because the greater tuberosity overlaps the humeral head on the internal rotation anteroposterior (AP) view, an external rotation AP projection is important to evaluate the greater tuberosity



Tyson & Hatem tangentially, separate from the humeral head.18 Because pain in the acute setting may preclude external rotation occasionally, Ogawa and colleagues15 advocate for a true lateral view for evaluation of the greater tuberosity.

Nondisplaced Radial Head or Neck Fracture The majority of elbow fractures in the adult patient are radial head and neck fractures, comprising approximately 33% to 50% of elbow fractures, about one-half of which are nondisplaced (Fig. 2).19 As a result, they are easily missed, which can lead to increased patient morbidity. The typical mechanism is a fall on an outstretched hand resulting in axial loading and valgus stress with radiocapitellar impaction.20 Because AP and flexed lateral radiographs alone have a high rate of missed elbow fracture in acute trauma, obtaining additional views has been emphasized, including internal and external

obliques as well as the radial head–capitellum view.21–23 Although there are a few published studies that question the usefulness of additional views of the elbow,24 most authors support either routine or selected use of supplemental views in the setting of acute injury. In a small series by Grundy and colleagues,22 the radial head–capitellum view yielded the diagnosis of radial head fracture when the traditional AP and lateral views did not in 21% of patients. These results validated an earlier study by Greenspan and colleagues,23 which demonstrated additional diagnostic information regarding fracture presence or extent in 20% of patients. Because the treatment of radial head fractures depends on not only confirmation of the fracture, but also on accurate characterization of the fracture, in our practice we routinely obtain oblique and radial head–capitellum views in the setting of trauma when a joint effusion is identified on a routine AP and lateral series.

Fig. 2. Radial head fracture. Fall on an outstretched hand. Anteroposterior (A) and lateral (B) views of the elbow are normal except for the subtle visualization of the uplifted posterior fat pad (black arrow), and “sail sign” of an uplifted anterior fat pad (white arrow). Subsequent external oblique (C) and radial head–capitellar (D) views show the intraarticular fracture line (dashed black arrow) of the radial head and crimped radial neck (dashed white arrow).

Easily Missed Fractures of the Upper Extremity Elbow joint effusion in the setting of trauma, as demonstrated on the lateral view by visualization of the posterior fat pad and/or an elevated anterior fat pad, traditionally is considered pathognomic for acute bony injury.25,26 Recent studies with MR imaging have confirmed fat pad displacement to be a sensitive sign of bony injury (95%) and occult fracture.27 Thus, after an elbow injury, recognition of a displaced fat pad should prompt further inquiry, including additional careful review of routinely obtained radiographs, obtaining additional views, or obtaining short interval follow-up radiographs. Although MR imaging is typically not used in the acute evaluation of isolated radial head fracture, it is the diagnostic test of choice to characterize comprehensively all coexistent injuries in the traumatic setting.27

Distal Radius Fracture Fractures of the distal radius are the most common fracture of the skeleton and account for an estimated 1 of every 6 acute fractures in the emergency setting (Fig. 3).28 The most common mechanism is a fall on an outstretched hand, particularly in younger patients.29 In the setting of acute trauma, a routine wrist radiographic series includes posteroanterior (PA), lateral, and pronated oblique views. Although the majority of distal radius fractures are not challenging in terms of identification, nondisplaced fractures, particularly of the radial styloid, are occasionally the exception. The radial styloid fracture is an oblique fracture, usually extending to the articular surface at the radiocarpal joint; colloquially, it is known as the chauffeur fracture. It is the result of axial loading or direct blow. Although these fractures are often displaced owing to pull from strong radiocarpal ligaments,30 occasionally they can be nondisplaced and subtle or imperceptible. Although there are several proposed classification systems regarding distal radial fractures, none are accepted universally. Indeed, it has been shown that interobserver variance between radiologists and orthopedists in fracture classification is poor.31 In this light, we prefer a detailed description of the fracture with reporting of salient features: fracture location and extent, accurate characterization of the amount of displacement of the articular component, degree of comminution, and identification of coexisting injuries. In particular, the degree of articular displacement has important treatment implications. Prior studies have shown that greater than 2 mm of intraarticular fracture displacement is associated with a high incidence of posttraumatic osteoarthritis.32

Scaphoid Fractures The scaphoid fracture is the most common carpal fracture (Fig. 4).33 It is also one of the most commonly missed fractures.34 As the primary osseous limiter to wrist extension, a fall on an outstretched hand with resultant hyperextension translates excessive force across the scaphoid, leading to injury.34 With up to 20% of scaphoid fractures occult radiographically, the diagnosis is often delayed, leading to an increased incidence of avascular necrosis (AVN), malunion, and nonunion.35 Scaphoid fractures are generally described by their anatomic location; 60% to 70% involve the scaphoid waist, 15% the proximal pole, 10% the distal pole, and 8% the distal articular surface.36 The primary blood supply to the scaphoid is via dorsal branches arising from the radial artery entering at the scaphoid waist.31 Thus, blood supply to the proximal pole is vulnerable. The incidence of AVN after scaphoid fracture is 30% after fractures through the middle third of scaphoid, increasing to nearly 100% after fracture through the proximal fifth.31,33 Displacement of fracture fragments also increases the risk of AVN. For similar reasons, tenuous blood supply of the proximal scaphoid contributes to lengthier healing times following acute fracture and increases the propensity for delayed healing or nonunion. Although beyond the scope of this discussion, MR imaging in particular has been considered an important tool for early detection of both scaphoid fractures and AVN, with the goal of minimizing the risk of, and sequelae from, AVN.31 As with the distal radius, radiographic evaluation begins with PA, lateral, and oblique views of the wrist, with the addition of a “scaphoid view” when clinical signs (anatomic snuffbox tenderness) and history alert the clinician to possible scaphoid fracture. The scaphoid view is a PA radiograph of the wrist centered over the scaphoid with the wrist in ulnar deviation. This view reduces the palmar flexion and foreshortening of the scaphoid seen on neutral views, improving visualization, especially of the waist, and likely increasing sensitivity of fracture identification. The presence of displacement and/or edema of the scaphoid fat stripe along its radial aspect has been advocated by some as a useful sign of occult scaphoid fracture,37 although this has been brought into question, because others have shown it to be a poor predictor of underlying pathology.38 In the setting of wrist injury and anatomic snuff box tenderness, it cannot be overemphasized that negative radiographs do not preclude scaphoid fracture. Most commonly, radiographic



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Fig. 3. Distal radius fracture. (A–F) 57F with radial styloid tenderness after falling on an outstretched hand. (A–C) Posteroanterior (PA), oblique, and lateral wrist radiographs at the time of presentation show very subtle soft tissue swelling (*) and hairline fracture (white arrows). (D–F) PA, oblique, and lateral wrist radiographs 2 weeks later. The fracture (arrows) is now readily apparent as a mixed lucent and sclerotic line owing to intramedullary callus deposition. (G–I) Different patient. Radial styloid fracture (thick white arrows) is barely perceptible on PA (G) and lateral (H) views, but is better seen on oblique (I).

follow-up is obtained for at least 2, and up to 6 weeks, after injury. Some authors have advocated for early MR imaging39 or CT40 to speed conclusive diagnosis.

Volar Plate Fractures The volar plate is a fibrous structure at the volar aspect of the joint capsule at each

Easily Missed Fractures of the Upper Extremity

Fig. 4. Scaphoid fracture. (A, B) Intraarticular fracture (arrow) of the distal pole is best visualized on the oblique view (B). (C, D) Scaphoid waist fracture (dashed arrow) in a different patient is visualized on the oblique view (D) only. (E–H) In a third patient, proximal pole fracture (dotted circle) is not seen on the routine series (E–G), but only the dedicated scaphoid view in ulnar deviation (H).

metacarpophalangeal and interphalangeal joint space (Fig. 5). It serves to prevent hyperextension.41 The distal aspect of the volar plate is characterized by a dense fibrocartilaginous

component centrally that attaches to the volar base of the phalanx. The lateral aspects of this distal attachment fuse with the fibers of the accessory collateral ligaments.41 During acute



Fig. 5. Volar plate fracture. (A–C) Posteroanterior (PA), oblique, and lateral views of the hand were obtained with attention to the little finger. Soft tissue swelling directs attention to the proximal interphalangeal joint. The volar plate fracture is difficult to visualize on the PA view owing to its position and characteristic mild flexion resulting in overlapping structures. Magnified oblique (D) and lateral (E) views show the characteristic appearance of a volar plate fracture fragment (white arrow) as a bony sliver of the radial aspect of the articular surface of the base of the middle phalanx on the oblique view (D) and as a small volar triangle on the lateral view. Commonly, the fracture is only seen on either the oblique or lateral; both need careful inspection.

Easily Missed Fractures of the Upper Extremity hyperextension, a distal volar plate injury can result in avulsion of the adjacent osseous attachment. Because there is almost always an ulnar component to the force, radial-sided avulsions predominate. In a series of 58 proximal interphalangeal joint volar plate fractures by Nance and colleagues,41 the majority of the patients (76%) were under the age of 30. Of the volar plate fractures in this series, 51% were sports-related injuries. Although the presence of a volar plate injury is typically readily apparent clinically, radiographs are performed to evaluate for an associated avulsion fracture. Complications related to volar plate fracture include posttraumatic osteoarthritis, flexion contraction/deformity, and joint instability. AP, lateral, and pronated oblique views should be performed when a volar plate injury is suspected. In the series by Nance and colleagues, approximately two-thirds of the fractures were best seen on the lateral view, and one-third best seen on the oblique view, which best shows the volar radial attachment site to the base of the middle phalanx.

OUT OF MIND, OUT OF SIGHT Scapula Fractures Scapula fractures are uncommon entities, representing only up to 1% of all fractures, and typically occur in association with other injuries in the setting of high energy trauma (Fig. 6).42 As such, they have the potential to be missed:

1 Owing to satisfaction of search when other more obvious injuries are identified 2 When only peripherally imaged directly in the acute trauma patient on other studies, such as a chest x-ray 3 When the scapula or shoulder is the primary area of concern but are not associated with a high-energy traumatic injury. Preferred radiologic evaluation begins with true AP and lateral scapular views to evaluate the glenoid rim and neck, scapular body, acromion, and coracoid, although not uncommonly only shoulder films are requested. As with greater tuberosity fractures, scapular fractures are increasingly identified as unsuspected injuries on shoulder MR imaging. The scapula is a complex bone, consisting of an articular component, the glenoid, and an unusually shaped body component to which muscles of the shoulder girdle attach. The combination of the complex geometry, obscuring adjacent structures, and the rarity of fracture contribute to the difficulty in detection of a scapular fracture. To add to this challenge, there are noteworthy anatomic variations that are confused easily with a scapula fracture, particularly in the young adult population most likely to suffer athletic or vehicular trauma. Basic awareness of the ossification pattern of the scapula is important to keep from mistaking epiphyseal lines for fractures, especially at the acromion and coracoid. What is more, the ossification centers may be asymmetric, rendering comparison films less useful, do not appear and fuse until

Fig. 6. Scapula fracture. Anteroposterior (AP; A) and lateral (B) views of the scapula. (A) The predominant finding on the AP is the V-shaped increased radiodensity owing to overlying fragments (*). Small cortical fragment (arrow) is present at the inferior scapular neck. Cortical disruption (arrow) and displaced fragment (*) are difficult to visualize through overlying humerus.



Tyson & Hatem late adolescence and young adulthood, and may remain unfused throughout adulthood. There are 2 to 3 acromial ossification centers that become apparent radiographically in the mid teenage years, and coalesce and fuse to the scapula spine by the age of 20 to 25 years.43 Failure of fusion results in an unfused accessory ossification center at the acromion, the os acromiale, which is seen in approximately 8% of the population.44 Likewise, the glenoid fossa ossifies from the coracoid base, deep portion of the coracoid process, scapular body, and the lower scapular pole; from the teen years into young adulthood, the glenoid border may normally be irregular.43 Although less commonly a radiologic quandary, the scapular inferior angle ossification center has a similarly late appearance and incorporation.

Coracoid Fractures The coracoid process serves as a point of attachment for several myotendinous and ligamentous structures and provides additional anterosuperior stability to the glenohumeral joint (Fig. 7).45 Coracoid fractures comprise 3% to 13% of all scapula fractures46 and are frequently missed initially.47 The mechanisms of fracture include a direct external force, contact from a dislocating humeral head, and avulsion by the short head of the biceps or coracobrachialis tendons. Coracoid base fractures are the most common type and are the result of a direct blow or anterior glenuhumeral dislocation. Fracture lines may extend into the upper glenoid, and can be confused with an accessory ossification center, as discussed. They are nondisplaced typically and treated nonsurgically. Fractures of the coracoid at the tip are avulsion fractures, and are also typically treated nonsurgically, even in the setting of significant displacement.45 In addition to the scapula and shoulder radiographic views described, additional views such as the axillary view and Stryker view, in which the arm is abducted and the x-ray beam is centered on the coracoid process with 10 cephalad angulation, can better isolate the coracoid from adjacent osseous structures.48 Weight bearing views in the setting of coexistent acromioclavicular separation may be helpful: the observation of a normal coracoclavicular distance in the setting of a high riding clavicle may be a clue to a coexistent coracoid fracture.43 In the setting of continued shoulder pain following glenohumeral dislocation and reduction, follow-up radiographs to evaluate for missed coracoid fracture have been advocated,49 although in our practice MR imaging is increasingly used for its ability to give a comprehensive review of both osseous and soft tissue integrity.

Acromion Fractures The acromion has 3 roles45: (1) articulate with the clavicle, (2) serve as a myotendinous and ligamentous attachment site, and (3) provide posterosuperior stability to the glenuhumeral joint (Fig. 8). Fractures of the acromion represent about 8% of all scapular fractures.50 These fractures most commonly occur in young to middle-aged adults as a result of high-energy trauma, and are often associated with other shoulder injuries.51 The acromion is most commonly injured via direct trauma; however, avulsion fractures and stress fractures have been reported.43,51 In addition to the standard radiographic views discussed previously, the Rockwood view (AP with caudal x-ray beam angulation) can be a useful supplement, in particular for evaluation of the inferior aspect of the acromion and the subacromial space.48 As mentioned, the unfused acromial ossification center can simulate an acromial fracture. Radiographic findings that favor an os acromiale over a fracture include rounded borders, positioning at, or superior to, the level of the posterior acromion on the AP view, and bilaterality.43 Kuhn and colleagues52 have proposed a classification system for acromial fractures, that although not used universally, is illustrative in terms of potential treatment implications. Nondisplaced (type I) and displaced fractures with preservation of the subacromial space (type II) are generally treated conservatively. Type III fractures narrow the subacromial space and are typically treated surgically.

Carpometacarpal Fracture Dislocation The carpometacarpal (CMC) articulations are a series of interlocking joints consisting of curved and irregular articular surfaces. Dislocations at the CMC joints are generally a result of high-energy trauma, and commonly are associated with neurovascular injury (Fig. 9).53 The injury pattern is generally that of dislocation with fracture involving the metacarpal bases, carpal bones, or both. Because of the undulating articular surfaces and overlap of structures on lateral radiographs, the CMCs are notoriously difficult to evaluate radiographically.43 In general, CMC fracture–dislocations with minimally displaced fractures that are able to maintain reduction can be treated with splinting or closed reduction and internal fixation. However, closed reduction may prove difficult if delayed, demonstrating the importance of early diagnosis.43 Particular attention should be directed ulnarly. Simultaneous fourth and fifth CMC dislocations are often subtle and initially missed on standard

Easily Missed Fractures of the Upper Extremity

Fig. 7. (A–C) Coracoid fracture. A 66-year-old man with acute anterior right shoulder pain after shooting a shotgun. Coracoid base fracture (white arrow) is faintly visualized owing to oblique projection on the anteroposterior (AP) internal rotation view (A), overlapping structures on the true AP external rotation projection (B), but is nicely demonstrated on the axillary projection (C). (D–F) Coracoid fracture and Hill–Sachs lesion. Chronic shoulder pain with history of prior anterior dislocations. Coracoid process fracture fragment (*) is distracted anterolaterally (double arrow) and can be seen on the true AP external rotation (D) and axillary (E) views. It is obscured on the AP internal rotation (F) view, which profiles a Hill–Sachs lesion (arrows) of the humeral head in the typical posterolateral location. (G, H) Coracoid fracture with acromioclavicular joint separation. AP radiograph (G) shows acromioclavicular joint separation with downward displacement (white double arrowhead). A normal coracoclavicular distance (black double arrowhead) should prompt careful evaluation of the coracoid. An unusual spike of cortical bone (white arrow) parallel to the scapular spine represents medial extension of the coracoid fracture (dashed white arrow) readily seen on sagittal CT reconstruction (H). (I) Coracoid and acromion ossification centers. Acromion (large black arrow) and coracoid (small black arrows) ossification centers can both persist into young adulthood and can mimic fractures. A contralateral view can be helpful.

radiographs54; however, they are unstable injuries with potentially severe consequences to their misdiagnosis.55 These dislocations are the most common of CMC dislocations and may occur after less severe trauma; a common mechanism is a

punch against a hard surface.55 We refer to these as “boxer fracture variants,” to emphasize the importance of looking for these whenever a search for the ubiquitous fourth and/or fifth metacarpal “boxer’s fractures” is negative.



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Fig. 8. Acromion fracture. The fracture (arrow) is almost completely obscured by the coracoid process on the anteroposterior (AP) internal rotation view (A), but can be visualized on the true AP (B) and axillary (C) projections.

A systematic approach as described by Fisher and colleagues54 may increase identification of CMC fracture dislocations. On the AP view, careful assessment for interruption of the normally smoothly undulating and parallel articular surfaces (disrupted “parallel M” sign), joint space asymmetry, articular cortex disruption, and articular surface overlap are keys to identifying an abnormality.54 The lateral view of the wrist demonstrates prominent dislocations at the CMC; however, owing to overlapping structures, more subtle subluxations can be missed easily. Particular attention should be directed to metacarpal angulation on the lateral projection: increased palmar angulation of the involved metacarpals is seen with the common dorsal dislocation.56 On the PA view, subtle metacarpal angulation radially can be assessed by evaluating metacarpal convergence, as described by Hodgson and Shrewing.55 In the normal patient, the long axes of the metacarpals (“the metacarpal cascade”) converge to a point just proximal to the distal radius articular surface. With CMC dislocations, the cascade lines either do not converge to a single point, or the point of convergence is displaced.55 Because of the importance of early and clinically appropriate treatment, either clinical suspicion alone or identification of a CMC fracture dislocation on initial radiographs should prompt consideration of CT evaluation to characterize more fully the injury and look for associated injuries.31 Associated fractures of the fourth metacarpal base, fifth metacarpal base, and/or hamate are often obscured on radiographs by overlapping structures and are better demonstrated on CT, analogous to tarsometatarsal Lisfranc injuries of the foot.

Hamate Fractures Fractures of the hamate represent approximately 2% of all carpal fractures (Fig. 10)57 and are generally categorized as either affecting the body or the

hook. Fractures involving the hamate body are less common than hook fractures, with variable mechanisms of injury, including fourth and fifth CMC dislocation, as discussed. Nondisplaced fractures can typically be treated conservatively, whereas displaced and nonreducible fractures require operative intervention.43 The hamate hook can be injured either via direct force or avulsion through the transverse carpal ligament.58 These injuries can occur as a result of a fall on an outstretched hand but most commonly occur in the grasping athlete: baseball players, golfers, tennis players, and so on. Hook of hamate fractures often present as a subacute injury with persistent pain, but can occur acutely. In minimally displaced hook fractures, conservative therapy with immobilization is used typically, although the rate of delayed healing and nonunion is high (50%).59,60 For displaced fractures or fractures associated with ulnar neuropathy, resection of the fracture fragment is often used rather than open reduction and internal fixation.57 Described findings on the PA view include failure to visualize the hook, indistinctness of its cortical margins, and sclerosis or double density.61,62 Oblique views should be scrutinized carefully dorsally and distally for fractures of the body. Nonetheless, standard radiographs of the wrist or hand are often negative for fracture, because the hook and the body of the hamate overlap.57 Numerous supplemental views have been advocated for evaluation of the hamate. The carpal tunnel view nicely depicts the hook of the hamate axially without overlap from osseous structures, and is likely the most widely added. Other authors favor modified lateral projections to see the entirety of the hook longitudinally without overlapping structures: these include the 30 tilted lateral view with palmar abduction of the thumb61 and a neutral lateral view with radial deviation of the wrist and thumb abduction.63

Easily Missed Fractures of the Upper Extremity

Fig. 9. Fracture dislocation of the fourth and fifth carpometacarpal joints. (A) Normal carpometacarpal joints (box) show smoothly undulating, parallel, and congruent articular surfaces. Posteroanterior (PA; B), oblique (C), and lateral (D) views of the wrist. Soft tissue swelling adjacent to the proximal fifth metacarpal (white arrow) directs attention to the fourth and fifth carpometacarpal joints (white box). The articular surfaces are overlapping owing to the coronally oriented, dorsally impacted shear fracture of the hamate (*) with double density on the PA and oblique views. A tiny fracture fragment is confirmed at the base of the fourth metacarpal (dashed arrow, D). Note characteristic volar angulation of the fourth and fifth metacarpals. (E–G) Spectrum of Boxer’s variant injuries. (E) Dorsal dislocation of the fourth and fifth carpometacarpal joints without fracture (box), with hamate flake fracture (short dashed arrow, F), and intraarticular fourth metacarpal base fracture (long dashed arrow, G).

Triquetrum Fractures Triquetrum fractures are the second most common carpal fracture following the scaphoid (approximately 15%; Fig. 11).64,65 Dorsal triquetrum fractures are most commonly owing to avulsion from the attachments of dorsal radiocarpal

ligaments. Transverse or sagittal fractures of the triquetral body are far less common, but have been described in association with a variety of different mechanisms, including crush injuries and perilunate fracture dislocations.57 The routine wrist series is usually sufficient for fracture identification. Dorsal triquetrum fractures



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Fig. 10. Hamate fracture. Golfer with acute pain after striking the ball. Routine wrist series normal. Posteroanterior view shown (A). Carpal tunnel view faintly visualizes the transverse fracture of the hook (dashed arrow), as seen on follow-up CT (axial C, sagittal D).

typically are visualized clearly on the lateral view as a small osseous fragment dorsally with overlying soft tissue swelling. Fractures of the triquetrum body may be more challenging to identify because there is significant osseous overlap on the PA and

lateral views. A 45 oblique radiograph can help to isolate the triquetrum from the adjacent pisiform, potentially improving fracture identification. Dorsal triquetrum fractures seldom require operative intervention; occasionally, symptomatic fractures

Fig. 11. Triquetrum fracture. Fracture is inapparent on the posteroanterior view (A). Fracture (short arrow) is only seen on the lateral view (B), with associated dorsal soft tissue swelling (long arrow).

Easily Missed Fractures of the Upper Extremity may necessitate excision of the bone chip for symptomatic relief.66

SATISFACTION OF SEARCH Fractures Associated with Glenohumeral Instability Although the shoulder complex provides a remarkable range of motion for the upper extremity, this flexibility comes with a cost: the glenohumeral joint is the most frequently dislocated joint in the body (Figs. 12 and 13).67 Concomitant injuries associated with glenohumeral dislocation include neurologic and vascular injury, injuries to the rotator cuff and glenoid labrum, and osseous injuries related to impaction, shear, and avulsive forces.43,68 Although the goal of prereduction and postreduction radiographs is to diagnose a dislocation and confirm reduction, an important secondary objective is to evaluate for these associated injuries.69 The humeral head, greater tuberosity, glenoid rim, acromion, and coracoid should be assessed carefully. The presence of these injuries has been associated with increased risk of recurrent dislocation.69 Greater tuberosity, coracoid, and acromial fractures have been discussed elsewhere in this article; humeral head fractures and glenoid rim fractures are discussed subsequently.

Evaluation of acute suspected shoulder dislocation typically includes radiographic evaluation of the shoulder, and typically includes an AP view in internal rotation, true AP (Grashey view) in external rotation, a lateral (scapular Y) view, and often an axillary or modified axillary view.48 Prereduction radiographs in the context of clinically obvious anterior shoulder dislocation may not always be necessary; some authors contend that they may be detrimental owing to increased time to reduction, additional radiation, and increased health care costs.70,71 Shuster and colleagues70 found that when an experienced emergency physician is confident of anterior shoulder dislocation, prereduction radiographs do not alter management. In anterior dislocations, impaction of the posterolateral aspect of the humeral head on the anteroinferior glenoid and can result in an osteochondral humeral head fracture known as a Hill– Sachs lesion. In contradistinction, in posterior dislocations the anteromedial humeral head impacts on the posterior glenoid and may develop a reverse Hill–Sachs lesion. Both of these fractures can be seen on AP views, and are often apparent on axillary projections. A Hill–Sachs lesion is best depicted on the AP view with internal rotation of the humerus as an area with lateral notching or flattening of the normal, circular appearance of

Fig. 12. Anterior dislocation sequelae of Hill–Sachs and Bankart lesions. The medial (white arrows) margin of the posterolateral impaction fracture (white arrows, A-C) of the humeral head is profiled on the internal rotation view (A). In external rotation (B) the inferior margin (dotted white arrows) of the V-shaped impaction is seen through overlying structures. Axial projections such as the Garth view (C) may also show the Hill–Sachs lesion (dotted and solid white arrows), but are particularly useful in identifying the osseous Bankart lesion (black arrow). Findings confirmed on subsequent MR arthrogram (D, axial fat-suppressed T1 and E, oblique sagittal T1 images).



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Fig. 13. Posterior dislocation sequelae of reverse Hill–Sachs lesion. History of prior posterior shoulder dislocations owing to seizures. (A) The anteroposterior view in external rotation shows a linear line of sclerosis (arrows) in the humeral head, the “trough sign,” which roughly parallels the humeral head articular surface. The impaction fracture (dashed arrows) is profiled on the axillary projection (B).

the humeral head in this position. The trough sign of a reverse Hill–Sachs lesion describes a sclerotic line parallel and lateral to the articular surface of the humerus on the AP view with humeral external rotation.69 Both of these fractures can worsen if the joint remains dislocated, as persistent muscle spasm can further exacerbate the impaction of the humeral head onto the glenoid.43 Owing to the same impaction mechanisms, associated fractures of the glenoid also occur. The osseous Bankart lesion describes such a lesion of the anterior inferior glenoid in the context of anterior shoulder dislocation.72 The reverse osseous Bankart lesion is the posterior glenoid fracture in the setting of posterior dislocation. Glenoid rim fracture fragments may be small, and, owing to overlapping structures, difficult to see radiographically. Postreduction radiographs are important not just to verify reduction but to look for these fractures: some fractures in the setting of shoulder dislocation are seen only on the postreduction series.73,74 Hendey and colleagues looked at 175 anterior shoulder dislocations and found 17 fractures (14 Hill–Sachs deformities, 2 Bankart fractures, and 1 greater tuberosity fracture) that were seen only on the postreduction views. In another study, Kahn and colleagues looked at 57 patients with anterior dislocations, and found that the although the majority of fractures associated with dislocation could be identified on prereduction views, more than one-third of fractures (37.5%) were seen only after postreduction imaging.

radial head fractures can be extremely subtle. Radial head fractures associated with the Essex–Lopresti fracture dislocation usually are not; they are typically comminuted (although not always) and impacted. This leads to radial shortening, resulting in interosseous membrane disruption and injury to the DRUJ, with subsequent DRUJ instability.75 They are included in this discussion because, although the fractured radial head may be apparent, the important, associated DRUJ injury can be easily missed. The totality of this injury is often missed initially in the setting of acute trauma because much of the focus is directed to the fractured radial head, and the symptoms in the wrist are often minimal in the acute stage.76 In addition, the radiographic features of distal radioulnar dislocation can be subtle. Although it has been reported that a greater than 5 mm discrepancy between the radioulnar distance on the injured versus noninjured wrist on lateral views is considered diagnostic for dislocation,77 in our experience this has been difficult to reproduce. Because the majority of Essex–Lopresti injuries require surgical treatment, and surgical outcomes are improved with early intervention,76 once the suggestion of possible distal radioulnar injury in the setting of a comminuted radial head fracture is raised, further investigation, including a focused physical examination, and dedicated CT should be considered. Owing to the subtlety of DRUJ subluxation, we prefer to image both wrists together and, if tolerated, in maximally supinated and pronated as well as neutral positions.

Essex–Lopresti Fracture–Dislocation

Carpal Instability and the Zone of Vulnerability

The Essex–Lopresti injury involves fracture of the radial head with dislocation of the distal radioulnar joint (DRUJ; Fig. 14). As discussed, nondisplaced

Perilunate dislocations and perilunate fracture dislocations are typically a result of a fall on an


Fig. 14. Essex–Lopresti. (A, B) Anteroposterior (A) and lateral (B) radiographs at presentation after a fall on an outstretched hand show mildly impacted intraarticular fracture of the radial head (solid white arrow). (C–E) On follow-up visit 1 month later, the patient complained of wrist pain and dorsal subluxation of the distal radioulnar joint (dashed white arrow) was suspected radiographically (D, E) and confirmed on CT (E).

Fig. 15. Trans-scaphoid perilunate fracture dislocation. (A–C) Posteroanterior (PA), oblique, and lateral views of the wrist. Scaphoid waist fracture is obvious on the PA and oblique (black arrows) views and is the site of disruption of the first and second carpal arcs of Gilula. The proximal pole scaphoid fragment (*) remains in normal apposition with the lunate and the distal pole (dashed line) is dislocated dorsally around the lunate with the remainder of the carpus. Note the pie slice–shaped configuration of the lunate–proximal pole scaphoid unit owing to mild palmar flexion.


Tyson & Hatem outstretched hand, with resultant hyperextension and axial loading. Unfortunately, they are missed radiographically in up to 25% of patients (Fig. 15).29 When left untreated, these injuries lead to unacceptable morbidity, including chronic pain and disability.78 Perilunate dislocations and perilunate fracture– dislocations have been described by Mayfield and colleagues,79 who described the mechanism of injury as a sequential process across the perilunate carpus in which both ligamentous and osseous injuries occur. This “zone of vulnerability” includes the radial styloid, trapezium, scaphoid, proximal capitate, proximal hamate, lunate border of the triquetrum, and ulnar styloid.80,81 These injuries occur in stages, beginning at the radial aspect of the wrist, and propagate in sequence ulnarly. As the injury progresses around the carpus, the potential for multiple fracture–dislocations increases. The transcaphoid fracture–dislocation is the most common of the carpal fracture–dislocation and typically involves the scaphoid waist, with the distal fracture fragment displacing with the rest of the dislocated carpus.29 This characteristic pattern of injury progression directs a search pattern for wrist fractures in the setting of carpal instability.

SUMMARY The radiographic assessment for upper extremity fractures remains a challenge. Missed diagnoses potentially have significant consequences for patients, clinicians, and radiologists. By reviewing 3 different categories of missed fractures—the common but challenging, the out of mind out of sight, and the satisfaction of search—we hope to have provided a framework for the reader to use not only when reviewing a study that initially seems to be normal, but for associated injuries when there is an obvious abnormality. Knowledge of what is commonly missed can only aid our diagnostic performance by prompting additional attention to these areas. The use of radiologic signs and the importance of additional views has been emphasized as an additional strategy to minimize mistakes.

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Easily Missed Fractures of the Upper Extremity.

Radiographs remain the mainstay for initial imaging of suspected fracture in the emergency setting. Missed fractures potentially have significant nega...
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